Seb 31 - Different type of blade play and how to fix it.

ac3boyz

ac3boyz

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1,157
Hello all,

I currently have a 31 with blade play that I don't understand nor do I know how to correct.

Subject is a large 31.
When closed, the blade is secure with no movement. When open and locked, there is also no movement in any direction.
However, when I'm opening or closing it, I can detect a small amount of loose movement along the arc of the blade's trajectory. It isn't side to side, just along its path. Maybe 1/16". It doesn't cause a problem, but it is a noticeable and weird feeling.

I have had this occur on CRK's in the past, but after taking them apart and reassembling them, the problem would be resolved. Don't know what, if anything I did to get it to stop.

Anyone know what might be happening and the appropriate fix?

Thanks!
 
ac3boyz said:
Hello all,

I currently have a 31 with blade play that I don't understand nor do I know how to correct.

Subject is a large 31.
When closed, the blade is secure with no movement. When open and locked, there is also no movement in any direction.
However, when I'm opening or closing it, I can detect a small amount of loose movement along the arc of the blade's trajectory. It isn't side to side, just along its path. Maybe 1/16". It doesn't cause a problem, but it is a noticeable and weird feeling.

I have had this occur on CRK's in the past, but after taking them apart and reassembling them, the problem would be resolved. Don't know what, if anything I did to get it to stop.

Anyone know what might be happening and the appropriate fix?

Thanks!
Click to expand...
I have a 21 that does this as well (if I'm understanding correctly), and I figure it's a tiny bit of play in the bushing. If I disassemble and re-grease everything it goes away for awhile, but comes back eventually. But like Bill said, it's not really an issue.
 
I have 3 sebenza 21’s and I believe they all do it. I know for a fact 2 of them do. I have also read of other people questioning the “so called” play and my opinion is that it is normal. You will never use the knife in the half opened position therefore it doesn’t really matter and not really a way to fix it. Just enjoy it.
 
If it really bothered you just contact CRK and see what they say. Like mentioned above I am not sure it is anything to be concerned about. I have some 21s, but never really noticed it.
 
jjg6319 said:
If it really bothered you just contact CRK and see what they say. Like mentioned above I am not sure it is anything to be concerned about. I have some 21s, but never really noticed it.
Click to expand...
Thanks for your input. It doesn't bother me, I mostly wanted to make sure it wasn't something related to my reassembly. From what everyone seems to say, it looks like I'm good to go.
 
I think some refer to it as "pivot lash" .

It's from the pivot (or pivot bushing) momentarily free spinning with the blade as it opens.

Some knives have it and some don't. Even some of my own that are built with identical parts, identical methods and the same bits/reamers. One might have it, the next not.

There are potential fixes but its not really worth worrying about.

It is not an indication of a problem or of a poorly made knife.
 
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This sounds like it might be the same as a small Inkosi I have had. If you open the blade part way and put your thumb on the flat, can you kinda jiggle the blade back and forth and get the noise? Mine was like that, and it was killing me just because it was so noisy opening and closing it.

I just sent it into CRK in February asking that they check it out to make sure there wasn't really an issue (plus servicing and reblasting the handles). It was done almost exactly a month later, and it seems to be fixed. They said they replaced all the hardware. The only cost was $20 to ship it back.
 
kreole said:
This sounds like it might be the same as a small Inkosi I have had. If you open the blade part way and put your thumb on the flat, can you kinda jiggle the blade back and forth and get the noise? Mine was like that, and it was killing me just because it was so noisy opening and closing it.
Click to expand...
Close, but there's no noise involved.

As I open or close the blade, if I stop anywhere along its path, there's just a very small amount in play until I continue.
I just wanted to make sure this wasn't a sign of pieces not being completely seated correctly, etc.
I'm not going to worry about it.
 
ac3boyz said:
Close, but there's no noise involved.

As I open or close the blade, if I stop anywhere along its path, there's just a very small amount in play until I continue.
I just wanted to make sure this wasn't a sign of pieces not being completely seated correctly, etc.
I'm not going to worry about it.
Click to expand...
Sounds like it might be the same just without a noise if I'm understanding. By blade play do you mean like if you pull/push the blade perpendicular to the handle that it has room to move? That's what I meant to say I could do with my thumb along the arc as well, but mine was enough it would click.

Here's a clip from before I sent it in. The clicking is the blade+pivot
https://imgur.com/a/p6Z8ybc

They didn't say it was some critical issue, and it was totally fine closed and fully open.
 
kreole said:
Sounds like it might be the same just without a noise if I'm understanding. By blade play do you mean like if you pull/push the blade perpendicular to the handle that it has room to move? That's what I meant to say I could do with my thumb along the arc as well, but mine was enough it would.

They didn't say it was some critical issue, and it was totally fine closed and fully open.
Click to expand...
No, it's along the arc of the blade path. I don't even know that I would consider it "play".
If I partially open the blade and stop, there just a little wiggle along that arc before I feel tension. It's so slight that it would probably be hard to catch in a video, but it is enough for me to notice.
 
Sounds like pivot play: the hole in the blade is a tiny bit too wide relative to the pivot (bushing in this case). Doesn't do any harm and can't be fixed, short of using a slightly wider bushing, or replacing the blade with one that has a smaller hole. My 31 has this, too, but I don't notice in normal use. Can only be felt by pushing/pulling on the blade while it's in between open and closed.
 
Blade Lab said:
Sounds like pivot play: the hole in the blade is a tiny bit too wide relative to the pivot (bushing in this case).
Click to expand...
Exactly.
You can feel this play before the blade comes to its final (open) position and the lock push the blade and lock it. But there is still a gap between the pin and the hole.

Blade Lab said:
Doesn't do any harm
Click to expand...
Probably not but I personally would be upset. For the price they ask they should figured out those tolerances.
 
Blade Lab said:
Agree, but it’s surprisingly common, even among pricier knives in my collection.
Click to expand...
.... as common as cutting prices in production, charge the same price for the final product and make more profit ... very common these days even with products marked as premium.
Or even more extreme; order some parts 'oversea' and cut production prices even more and make even more profit.
 
TheOne45 said:
.... as common as cutting prices in production, charge the same price for the final product and make more profit ... very common these days even with products marked as premium.
Or even more extreme; order some parts 'oversea' and cut production prices even more and make even more profit.
Click to expand...
Yep, you've got them pegged... 🤦‍♂️ Forget the fact that they just moved all of their fasteners to in house production.

I'm pretty sure that the explanation I've seen for this is, that there's some space required in the pivot for it to be able to move. It's a folder, if you don't want blade play anywhere then get a sheath knife.
 
Lots of folders have this that I have noticed over the years. But pivot lash and tolerance stacking are real and difficult to counter. I cannot imagine how extra expensive folders would be if every pivot needed to hand selected and fitted to avoid lash and still operate as a pivot with just the right action.
 
If the knife locks up solidly when closed and open, it doesn't matter what the blade does in between those positions.
You guys want "flipper" knives, and flippers need to be as loose as possible when opening.
 
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